1. Field of the Invention
The present invention is in the field of downhole equipment, often used in oil and gas well drilling and downhole equipment recovery, the operation of which is accompanied by repetitive pressure pulses in the drilling fluid, such as jarring devices. More specifically, it is a device that absorbs pressure pulses in the drilling fluid, generated by the rapid impacts which can be delivered by a tool such as a jarring tool, for the purpose of loosening a stuck object.
2. Background Art
In well operation, there is often a need for jarring, impact or vibration devices to move downhole stuck members. Jars are typically included in a pipe or work string to provide upward or downward impacts when activated. The impact is typically initiated when some type of valve or other triggering device in the tool triggers an action which applies stored energy in the form of an impact delivered to the stuck object.
This type of tool is usually supplied with a flow of drilling fluid delivered through the work string by a pump at the surface of a well site. The jarring tool often functions by momentarily interrupting the flow of drilling fluid, as these momentary interruptions of drilling fluid flow can be used to move valving members within the jarring tool. The frequent, repeated interruption of drilling fluid flow often results in the generation of pressure pulses in the drilling fluid, at the jarring tool. These pressure pulses travel back up the fluid column within the work string, to the surface at the well site.
At the surface, these pressure pulses are absorbed by equipment used in the delivery of drilling fluid downhole, such as the pump, standpipe, flex hose, swivel, and all the related fittings. In some such cases, the flex hose has been known to deflect sharply, and fittings have been known to fail. A pressure attenuating device on the pump would not likely adequately protect all the affected equipment.
It would be desirable, then, to have a means for attenuating these pressure pulses, to prevent damage to the well drilling or workover equipment. Further, it would be highly desirable to attenuate the pressure pulses at a downhole location close to the jarring tool, thereby protecting the majority of the work string from damage, as well as protecting the surface equipment.